viết phương trình sử dụng While do để tính tổng
C=1/2+1/3+1/4....+1/N
D=1/1x2+1/2x3+1/3x4...
+1/49x50
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a: \(A=\dfrac{5}{7}-\dfrac{2}{7}+\dfrac{8}{11}+\dfrac{3}{11}+\dfrac{1}{2}=\dfrac{3}{7}+\dfrac{1}{2}+1=\dfrac{6+7+14}{14}=\dfrac{27}{14}\)
b: \(B=\dfrac{11}{17}+\dfrac{6}{17}-\dfrac{8}{19}-\dfrac{30}{19}+\dfrac{-3}{4}=1-2-\dfrac{3}{4}=-1-\dfrac{3}{4}=-\dfrac{7}{4}\)
c: \(C=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{49}-\dfrac{1}{50}=\dfrac{49}{50}\)
khó quá sai thì thôi nha
= 1/1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + .... + 1/49 - 1/50
= 1/1 - 1/50
= 49/50
1/1.2 + 1/2.3 + 1/3.4 +.....+ 1/49.50
= 1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 +......+ 1/49 - 1/50
= 1 - 1/50
= 49/50
A=\(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{49.50}\)
A=\(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{49}-\frac{1}{50}\)
A=\(1-\frac{1}{50}\)
A=\(\frac{49}{50}\)
Ta có công thức \(\frac{a}{b.c}=\frac{a}{c-b}.\left(\frac{1}{b}-\frac{1}{c}\right)\)
Dựa vào công thức trên, ta có
\(\frac{1}{1.2}=\frac{1}{2-1}.\left(1-\frac{1}{2}\right)\)
\(\frac{1}{2.3}=\frac{1}{3-2}.\left(\frac{1}{2}-\frac{1}{3}\right)\)
............................................
\(\frac{1}{49.50}=\frac{1}{50-49}.\left(\frac{1}{49}-\frac{1}{50}\right)\)
\(A=1.\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+....+\frac{1}{49}-\frac{1}{50}\right)\)
\(\Rightarrow A=1-\frac{1}{50}=\frac{49}{50}\)
chắc chắn bạn ạ, ai thấy đúng hì ủng hộ nha
\(A=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{49.50}=1-\frac{1}{50}=\frac{49}{50}\)\(\frac{49}{50}\)
Ta có :
\(A=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{49.50}\)
\(A=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{49}-\frac{1}{50}\)
\(A=1-\frac{1}{50}\)
\(A=\frac{49}{50}\)
Vậy \(A=\frac{49}{50}\)
Chúc bạn học tốt ~
= 1/1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + ... + 1/49 - 1/50
= 1/1 - 1/50
= 49/50
A = 1/1 - 1/2 + 1/2 - ....-1/50 = 1-1/50 = 49/50
B = 1/2 . (1/3 - 1/7 + 1/7 -.....-1/27) = 1/2. (1/3 - 1/27)
B = 1/2. 8/27 = 4/27
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{49}-\frac{1}{50}\)
\(=1-\frac{1}{50}\)
\(=\frac{49}{50}\)
\(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+.........+\frac{1}{49.50}\)
\(=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+.......+\frac{1}{49}-\frac{1}{50}\)
\(=\frac{1}{1}-\frac{1}{50}\)
\(\frac{50}{50}-\frac{1}{50}=\frac{49}{50}\)
Vì \(\frac{49}{50}<1\Rightarrow\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{49.50}<1\)
program TinhTongWhileDo;
var
n, i: integer;
S: real;
begin
write('Nhap so n: ');
readln(n);
S := 0;
i := 1;
while i <= 2*n do
begin
S := S + 1/i;
i := i + 1;
end;
writeln('Tong S=1/1+1/2+1/3+1/4+...+1/2n la: ', S:0:2);
readln;
end.
uses crt;
var c,d:real;
i,n,j:integer;
begin
clrscr;
write('Nhap n='); readln(n);
i:=1;
c:=0;
while i<=n do
begin
i:=i+1;
c:=c+1/i;
end;
writeln('C=',c:4:2);
d:=0;
j:=1;
while j<=49 do
begin
d:=d+1/(j*(j+1));
inc(j);
end;
writeln('D=',d:4:2);
readln;
end.